U.S. patent number 5,632,143 [Application Number 08/262,503] was granted by the patent office on 1997-05-27 for gas turbine system and method using temperature control of the exhaust gas entering the heat recovery cycle by mixing with ambient air.
This patent grant is currently assigned to Ormat Industries Ltd.. Invention is credited to Uriyel Fisher, Yoel Gilon, Joseph Sinai.
United States Patent |
5,632,143 |
Fisher , et al. |
May 27, 1997 |
Gas turbine system and method using temperature control of the
exhaust gas entering the heat recovery cycle by mixing with ambient
air
Abstract
A gas turbine system with a heat recovery cycle includes a gas
turbine unit that produces hot exhaust gases which are applied to a
heat recovery heat exchanger containing a working fluid responsive
to applied hot gases for producing vaporized working fluid and
cooled gases which are vented. A turbine connected to a generator
and responsive to the vaporized working fluid generates power and
produces expanded working fluid. A condenser condenses the expanded
vaporized working fluid to condensate which is returned to the heat
recovery heat exchanger. A control device (94) controls the
temperature of the applied hot gases, based on a sensed temperature
(89) and include mixer apparatus (87) for mixing ambient air with
the hot exhaust gases and producing a mixture of hot exhaust gases
and ambient air before the mixture is applied to the heat recovery
heat exchanger.
Inventors: |
Fisher; Uriyel (Haifa,
IL), Sinai; Joseph (Ramat Gan, IL), Gilon;
Yoel (Jerusalem, IL) |
Assignee: |
Ormat Industries Ltd. (Yavne,
IL)
|
Family
ID: |
22991738 |
Appl.
No.: |
08/262,503 |
Filed: |
June 20, 1994 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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261045 |
Jun 14, 1994 |
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Current U.S.
Class: |
60/39.182;
60/39.181; 60/39.5 |
Current CPC
Class: |
F01K
23/10 (20130101); Y02E 20/16 (20130101) |
Current International
Class: |
F01K
23/10 (20060101); F02C 006/00 () |
Field of
Search: |
;60/39.181,39.182,39.183,39.2,39.29,39.5,262,726 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0367109 |
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Jan 1923 |
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DE |
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026710 |
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Dec 1982 |
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JP |
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Primary Examiner: Casaregola; Louis J.
Assistant Examiner: Kim; Ted
Attorney, Agent or Firm: Sandler; Donald M.
Parent Case Text
This application is a continuation-in-part of application Ser. No.
08/261,045 filed Jun. 14, 1994, now abandoned.
Claims
We claim:
1. A method for using a gas turbine system that drives a
utilization device and produces hot exhaust gases;
a) mixing ambient air with said hot exhaust gases for producing hot
gases having a reduced temperature, and transferring heat from the
hot gases having a reduced temperature to a working fluid contained
in a heat recovery heat exchanger for producing vaporized working
fluid and cooled exhaust gases that vent to the atmosphere;
b) expanding said vaporized working fluid in a vapor turbine
included in a turbogenerator for generating power and from which
expanded vaporized working fluid exits; and
c) condensing said expanded vaporized working fluid and pumping the
condensate back to said heat recovery heat exchanger.
2. A method according to claim 1 including selectively switching
said hot exhaust gases between said heat exchanger and a by-pass
stack.
3. A method according to claim 1 including controlling the amount
of ambient air that is mixed with the exhaust gases.
4. A method according to claim 3 including sensing the temperature
of said hot gases having a reduced temperature before heat therein
is transferred to said working fluid, and controlling the amount of
said ambient air that is mixed with the hot exhaust gases in
response to the sensed temperature.
5. A method according to claim 1 wherein said vaporized working
fluid is produced by first preheating said condensate with said
exhaust gases.
6. A method according to claim 1 wherein the temperature of the hot
exhaust gases is reduced before heat therein is transferred to said
working fluid by forced injection of ambient air into said hot
exhaust gases.
7. A method according to claim 1 wherein the step of condensing
said expanded vaporized working fluid is carried out by cooling the
expanded vaporized working fluid with air.
8. A gas turbine system with a heat recovery cycle comprising:
a) a gas turbine unit for driving a utilization device and
producing hot exhaust gases;
b) a heat recovery heat exchanger containing a working fluid
responsive to applied hot gases for producing vaporized working
fluid and cooled gases which are vented;
c) a vapor turbine connected to a generator and responsive to said
vaporized working fluid for generating power and from which
expanded working fluid exits;
d) a condenser for condensing said expanded vaporized working
fluid, and a pump for returning working fluid condensate to said
heat recovery heat exchanger; and
e) a combiner for combining ambient air with said hot exhaust gases
and producing a mixture of hot exhaust gases and ambient air, said
combiner being constructed and arranged to apply said mixture to
said heat recovery heat exchanger; and
f) a temperature sensor for sensing the temperature of said mixture
and producing control signals, said combiner being responsive to
said control signals for controlling the ratio of exhaust gases to
ambient air in said mixture.
9. A gas turbine system according to claim 8 wherein said working
fluid is water.
10. A gas turbine system according to claim 9 wherein said
condenser includes an indirect contact heat exchanger containing an
organic fluid responsive to said expanded vaporized working fluid
for producing vaporized organic fluid, an organic vapor turbine
responsive to said vaporized organic fluid for generating power and
from which expanded vaporized organic fluid exits, an air-cooled
condenser for condensing said expanded vaporized organic fluid into
condensate, and means for returning the last mentioned condensate
to said indirect contact heat exchanger.
11. A gas turbine system according to claim 8 wherein said working
fluid is an organic fluid.
12. A gas turbine system according to claim 11 wherein said
condenser is an air cooled organic vapor condenser.
13. A gas turbine system according to claim 1 including a
positionable valve associated with said combiner for controlling
the amount of ambient air mixed with said hot exhaust gases.
14. A gas turbine system according to claim 13 including a valve
controller responsive to said control signals for controlling the
position of said valve for controlling the amount of ambient air
mixed with said hot exhaust gases.
15. A gas turbine system according to claim 1 wherein said heat
recovery heat exchanger includes a vaporizer heat exchanger
component and a preheater component arranged so that said vaporizer
component encounters said hot applied gases before the latter
encounter said preheater component.
16. A gas turbine system according to claim 15 wherein said heat
recovery heat exchanger includes a tubular body having an inlet
section into which said hot exhaust gases enter, and said control
means includes an injector having a free end opening into said
inlet section and through which ambient air is supplied, and fan
means for drawing ambient air through said injector.
17. A gas turbine system according to claim 16 wherein said fan
means is located upstream of said injector.
18. A gas turbine system according to claim 16 wherein said fan
means is located downstream of said injector.
19. A gas turbine system according to claim 15 wherein said tubular
body of said heat recovery heat exchanger includes an outlet
section into which said cooled gases enter before being vented to
the atmosphere.
20. A gas turbine system according to claim 15 wherein said working
fluid is an organic fluid, and said heat recovery heat exchanger
includes, in addition to said vaporizer heat exchange component and
said preheater component, a vaporizer tank that receives heated
organic liquid from said vaporizer heat exchange component, and
preheated organic condensate from said preheater, and delivers
vaporized organic fluid to said turbine, and liquid organic fluid
to said vaporizer heat exchanger component.
21. A gas turbine system according to claim 1 including a
connection for selectively switching said hot exhaust gases
produced by said gas turbine unit between said heat recovery heat
exchanger and a by-pass stack.
22. A gas turbine system according to claim 8 wherein said
utilization device is a gas compressor for compressing gas and
producing compressed gas.
23. A gas turbine system according to claim 22 wherein said gas
compressor includes a cooler for cooling said compressed gas, said
cooler being constructed and arranged to transfer heat from said
compressed gas to said working fluid condensate before the latter
is returned to said heat recovery heat exchanger.
24. A gas turbine system with organic fluid heat recovery cycle
comprising:
a) a gas turbine unit for driving a utilization device and
producing hot exhaust gases;
b) a heat recovery heat exchanger containing an organic fluid
responsive to applied hot gases for producing vaporized organic
fluid and cooled gases that are vented
c) an organic vapor turbine responsive to said vaporized organic
fluid for driving a generator and generating power and from which
expanded organic vapor exits;
d) an air-cooled condenser for condensing said expanded vaporized
organic fluid, and a pump for returning organic fluid condensate to
said heat exchanger;
e) an adjustable connection for selectively switching said hot
exhaust gases between said heat recovery heat exchanger and a
by-pass stack; and
f) control means to mix ambient air with said hot gases to form a
mixture for controlling the temperature of said mixture; and
g) means for applying said mixture to said heat recovery heat
exchanger.
25. A gas turbine system with a heat recovery cycle comprising:
a) a gas turbine unit for driving a utilization device and
producing hot exhaust gases;
b) a heat recovery heat exchanger containing a working fluid
responsive to applied hot gases for producing vaporized working
fluid and cooled gases which are vented;
c) a vapor turbine connected to a generator and responsive to said
vaporized working fluid for generating power and from which
expanded working fluid exits;
d) a condenser for condensing said expanded vaporized working fluid
to condensate, and a pump for returning working fluid condensate to
said heat recovery heat exchanger; and
e) control means for controlling the temperature of said applied
hot gases, said control means including mixing means for mixing
ambient air with said hot exhaust gases and producing a mixture of
hot exhaust gases and ambient air before the mixture is applied to
the heat recovery heat exchanger and enters into heat exchange
relationship with said working fluid, said mixing means being
responsive to the temperature of said mixture for controlling the
ratio of exhaust gases to ambient air in said mixture.
26. A gas turbine system with a heat recovery cycle comprising:
a) a gas turbine unit for driving a utilization device and
producing hot exhaust gases;
b) heat recovery heat exchanger means containing working fluid
responsive to applied hot gases for producing vaporized working
fluid and cooled gases that are vented;
c) a vapor turbine responsive to said vaporized working fluid for
driving a generator and generating power and from which expanded
working fluid exits;
d) an air-cooled condenser for condensing said expanded working
fluid to condensate, and a pump for returning said condensate to
said heat recovery heat exchanger; and
e) control means for controlling the temperature of said applied
hot gases before the latter are applied to said heat exchanger
means, including mixing means for mixing ambient air with said hot
exhaust gases before the gas mixture of hot exhaust gases and
ambient air is applied to the heat recovery heat exchanger and
enters into heat exchange relationship with said water.
27. A gas turbine system according to claim 26 including a
connection for selectively switching said hot exhaust gases from
said gas turbine unit between said heat exchanger and a by-pass
stack.
Description
1. TECHNICAL FIELD
This invention relates to a gas turbine system that includes a heat
recovery cycle, and to a method for using the same.
2. BACKGROUND OF THE INVENTION
Gas turbines have been used for producing power in many
installations around the world. Often, the exhaust gases of the gas
turbine are merely exhausted into the atmosphere. For example, high
pressure natural gas transmission pipelines are conventionally used
for transporting gas from production fields to customers remotely
located from the fields. Gas compressors feeding such pipelines
usually are powered by a gas turbine, and optionally, a heat
recovery cycle can be employed to reduce the net power requirement
by converting waste heat in the hot exhaust gases from the turbine
into electricity. An installation of this type is illustrated
schematically in FIG. 1 which shows a two stage air compressor
producing compressed air that is supplied to a gas turbine coupled
to a utilization device, such as a gas compressor. In such an
installation, a portion of the compressed gas supplied by the
compressor is bled into a combustor and burned in the compressed
air before the resultant combustion gases are applied to the gas
turbine.
The temperature of the hot gases that exit the gas turbine can be
about 450.degree. C., and these gases usually contain sufficient
heat to make heat recover economically justifiable. Conventionally,
the exhaust gases are applied to an indirect contact heat exchanger
containing water which is vaporized. The resultant steam is
supplied to a steam turbine coupled to a generator that produces
electricity, and expanded steam that exits the turbine. The
expanded steam is condensed in a condenser that usually is supplied
with cooling water from a pond associated with a cooling tower.
During cold weather, ambient temperature may drop below freezing
causing the cooling water and the steam condensate to freeze thus
interfering with the functioning of the condenser and the cooling
tower. When this occurs, operation of the heat recovery cycle must
be terminated.
Recent improvements in organic vapor turbine design and
construction have suggested that an organic vapor turbine using an
air-cooled condenser might be used to replace the steam turbine in
the installation described above. This would have the advantage of
permitting the heat recovery cycle to remain operational during the
coldest weather. However, the high temperature of the exhaust gases
and the characteristics of organic fluids (e.g., pentane) used in
organic vapor turbine cycles raises the possibility that a
relatively hot portion of the heat exchanger could result in carbon
formation and deposition due to the excess heating of the organic
fluid by the hot exhaust gases.
It is therefore an object of the present invention to provide a new
and improved gas turbine system with heat recovery cycle and a
method for using the same which overcomes or substantially
ameliorates the problem described above.
BRIEF DESCRIPTION OF THE INVENTION
The present invention provides a heat recovery cycle for a gas
turbine system that includes a gas turbine unit for driving a
utilization device and producing hot exhaust gases, and a heat
recovery heat exchanger containing a working fluid, preferably an
organic fluid, which is responsive to applied hot gases for
producing vaporized working fluid and cooled gases which can be
vented to the atmosphere. When an organic working fluid is used, an
organic vapor turbine connected to a generator and responsive to
the vaporized organic fluid generates power and produces expanded
organic vapor that exits the turbine. The expanded vaporized
organic fluid is condensed in a condenser, and the condensed
organic fluid is returned to the heat recovery heat heat exchanger
by a pump. When ambient temperatures are below the freezing
temperature of water, an air cooled organic vapor condenser is
used. The temperature of the hot gases applied to the heat recovery
heat exchanger is controlled by a controller which includes a mixer
for mixing ambient air with the hot exhaust gases for producing a
mixture of hot exhaust gases and ambient air before the mixture is
applied to the heat recovery heat exchanger and enters into heat
exchange relationship with said organic fluid. Thus, the
temperature of the exhaust gases applied to the heat exchanger may
be reduced from, for example, around 450.degree. C. to around
300.degree. C.
To control the amount of ambient air mixed with the hot exhaust
gases, the controller may include a selectively positionable valve,
such as a flap valve, for controlling the amount of ambient air
that is mixed with the hot exhaust gases. In such case, the
controller may include a temperature sensor for sensing the
temperature of the applied hot gases, and a valve controller
responsive to the temperature sensed by said temperature sensor for
controlling the position of the valve, and thus the amount of
ambient air mixed with the hot exhaust gases.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present invention are described by way of
example with reference to the accompanying drawings wherein:
FIG. 1 is a schematic block diagram of a conventional gas turbine
system into which a steam-based heat recovery cycle is
integrated;
FIG. 2 is a schematic block diagram of a gas turbine system with an
organic fluid heat recovery cycle according to the present
invention;
FIGS. 3A, 3B, and 3C are schematic elevation sectional diagrams
showing details of three configurations of a heat exchanger
according to the present invention;
FIG. 4 is a schematic block diagram of a gas turbine system with a
steam-based heat recovery cycle into which the present invention is
incorporated; and
FIG. 5 is a schematic block diagram of a gas compressor operated by
a gas turbine for the purpose of showing an example of the
utilization of the heat in the intercoolers of the compressors of
the gas turbine and of the gas compressors for generating power in
accordance with the present invention.
DETAILED DESCRIPTION
Referring now to the drawings, reference numeral 10 designates a
gas turbine system according to the prior art into which is
incorporated a steam-based heat recovery cycle. System 10 includes
conventional gas turbine unit 12 comprising low and a high pressure
compressors 14, 16 coupled by shaft 17 to gas turbine 18. Ambient
air is applied to low pressure compressor 14, compressed, and
applied to high pressure compressor 16.
The compressed air is applied to combustor 20 wherein fuel is
burned producing high temperature gases that are applied to turbine
18 wherein expansion takes place. Energy extracted from the high
temperature gases by their expansion in the turbine drives
utilization device 22 which may be a gas compressor associated with
a gas pipeline (not shown). The expanded gases that exit from the
exhaust of turbine 18 have a temperature, which can be around
450.degree. C., for example, or higher or lower, depending on the
characteristics of the gas turbine. Heat is extracted from the hot
exhaust gases in heat recovery cycle apparatus 23 which includes
indirect heat recovery heat exchanger 24 to which the hot exhaust
gases are applied.
Heat exchanger 24 contains water which is vaporized by the heat
contained in the hot exhaust gases which are cooled to around
120.degree. C. by the heat exchange process that takes place
between the hot exhaust gases and the water in heat exchanger 24.
The cooled exhaust gases are vented to the atmosphere, as the steam
produced by heat recovery heat exchanger 24 is applied to steam
turbine 26 coupled to generator 27. The steam expands in turbine 26
driving the generator and producing expanded steam that exhausts
into indirect steam condenser 28 cooled by water supplied from
cooling tower 30. Pump 31 returns condensate produced by condenser
28 to heat exchanger 24.
When low ambient temperatures causes freezing of the water
associated with cooling tower 30, and of steam condensate produced
by steam condenser 28, apparatus 23 will be unable to operate; and
the heat recovery cycle must be shut down. This situation can be
averted by utilizing an organic fluid heat recovery system having
an air-cooled condenser because common organic working fluids, such
as hydrocarbon-based fluids, for example pentane, have a very low
freezing point and can be used under winter conditions found in
most places in the world. Such organic fluids may form carbon
deposits at relatively high temperatures with the result that the
heat exchanger design must take into account the possibility of
carbon formation or production from the working fluid particularly
when the heat exchange fluid has a temperature of around
450.degree. C. or greater.
Apparatus 40 shown in FIG. 2 takes into account the possibility of
carbon production from the organic fluid, but in a way that imposes
less stringent demands on the design of the heat exchanger.
Specifically, apparatus 40 incorporates control means 42 for
controlling the temperature of the hot gases that are applied to
heat exchanger 44 such that the temperature of the gases that enter
into heat exchange relationship with the organic fluid is reduced.
Specifically, the temperature of the exhaust gases is reduced by
mixing ambient air with the hot exhaust gases before the mixture
enters into heat exchange relationship with the organic fluid. For
example, the reduced temperature may be about 300.degree. C.
Apparatus 40 includes gas turbine unit 12A similar to unit 12 shown
in FIG. 1 for driving utilization device 22A, which may be a gas
compressor, and producing hot exhaust gases in line 41. Heat
recovery heat exchanger 44 containing an organic fluid, e.g.,
pentane, in the form of n-pentane or iso-pentane, is responsive to
the applied hot exhaust gases for producing vaporized organic fluid
in output line 45, and cooled exhaust gases in line 43 which are
vented to the atmosphere through a suitable stack. Organic vapor
turbogenerator 46, which includes organic vapor turbine 47 coupled
to electric generator 48, is responsive to vaporized organic fluid
in line 45 for generating power and producing expanded organic
vapor in line 49 connected to the exhaust of turbine 47. Condenser
50, which is air-cooled, serves to condense the expanded vaporized
organic fluid that exits turbine 47, and pump 52 returns the
organic fluid condensate to heat recovery heat exchanger 44 via
line 53.
Because of the relatively high temperature of the exhaust gases
that enter into heat exchange relation with the organic fluid in
the heat exchanger, the preferred construction of heat recovery
heat exchanger 44 includes preheater component 54, and vaporizer
component 55 which has vaporizer heat exchange portion 56 for
receiving the hot exhaust gases, and vaporizer drum 57. Portion 56
contains organic fluid in its liquid phase allowing an orderly
transfer of heat to the organic fluid without pockets of vapor
forming, thus promoting the efficient transfer of heat to the
organic fluid. After the heated liquid is transferred by the
operation of pump 58 from portion 56 to drum 57 via line 59, the
heated liquid vaporizes in the drum, and the vaporized organic
fluid flows via line 45 to turbine 47.
After giving up heat to the liquid organic fluid in portion 56, the
gases, somewhat reduced in temperature, encounter obtained
preheater component 54 containing organic fluid condensate from
condenser 50 via line 53 by reason of the operation of pump 52.
Additional heat is extracted from the gases in preheater component
54 preheating the organic fluid condensate which flows via line 60
to drum 57 which supplies preheated liquid to portion 56 of the
vaporizer. The gases are cooled by this encounter to about
120.degree. C. and are vented to the atmosphere.
While the use of an organic working cycle is particularly
advantageous under the conditions where ambient temperatures are
below the freezing point of water, a heat recovery cycle based on
an organic working fluid of the type previously mentioned also can
be advantageous even at ambient temperatures higher than the
freezing point of water. In such conditions, condenser 50 can be
air or water cooled and the organic fluid turbine will be much
smaller due to the larger difference in specific volume between
steam and organic vapor at the same temperature. In addition, among
other things, the condensing pressure usually will be above
atmospheric pressure.
The operation of control means 42 is illustrated in FIGS. 3A-C in
connection with three embodiments of heat recovery heat exchanger
44. Heat recovery heat exchanger 44A in FIG. 3A includes tubular
body 60 having inlet section 62 connected to exhaust duct 63 of the
gas turbine and into which hot exhaust gases enter. Preferably, the
heat recovery heat exchanger also includes outlet section 64 by
which body 60 is connected to stack 65 through which the exhaust
gases, after being cooled by giving up heat to vaporizer component
55 and to preheater component 54, are vented to the atmosphere.
Control means 42 associated with heat exchanger 44A also includes
injector 66 having an output end 67 that opens into inlet section
62, section 68 having input end 69 open to ambient air, and fan 70A
for drawing ambient air through injector 66 and into the heat
recovery heat exchanger. The control means also includes a
selectively positionable valve 71, e.g., a flapper valve, located
in section 68.
Preferably, the control means also includes temperature sensor 72
located in the region where the hot exhaust gases from the turbine
exhaust mix with ambient air exiting the injector for sensing the
temperature of the gases entering heat recovery heat exchanger 44.
In this manner, the temperature of the gases is sensed before they
are applied to the components 55 and 54 of the heat exchanger,
i.e., before heat in the gases is transferred to the organic fluid
in the vaporizer and preheater components of the heat
exchanger.
Temperature sensor 72 produces a control signal related to the
temperature difference between the temperature of the gases
entering heat recovery heat exchanger 44A and the set temperature
for these gases before any heat transfer takes place; and this
control signal is applied to valve controller 42A which controls
the position of valve 71. In this manner, the volume of ambient air
injected into the hot exhaust gases, and thus the temperature of
the mixture of air and exhaust gases can be controlled in
accordance with a desired set-point temperature. For example, if
the temperature of the exhaust gases that exit the gas turbine is
about 450.degree. C., the temperature of the mixture could be
selected as about 300.degree. C.; and valve controller 42A would be
effective to position valve 71 such that the selected temperature
would be achieved. In such case, the likely temperature of the
mixture of air and exhaust gases after the mixture ends its heat
exchange relationship with the preheater component of the heat
recovery heat exchanger, will be about 120.degree. C.
Heat recovery heat exchanger 44B shown in FIG. 3B is similar to
heat recovery heat exchanger 44A except that the fan, by which
forced air is injected into the exhaust gases before they enter
into heat exchange relationship with the organic fluid, is located
downstream of the injector rather than upstream as in the case of
heat recovery heat exchanger 44A. That is to say, fan 70B is
located in the vicinity of outlet section 64 of the heat exchanger
rather than in section 68. Otherwise, the operation of heat
recovery heat exchanger 44B is the same as the operation of heat
recovery heat exchanger 44A.
The purpose of installations shown in FIGS. 3A and 3B is to reduce
the backpressure on the gas turbine exhaust with the aid of fan 70A
shown in FIG. 3A and fan 70B shown in FIG. 3B. Thus, each of heat
recovery heat exchangers 44A and 44B involve forced air injection.
Heat recovery heat exchanger 44C differs from each of heat recovery
heat exchangers 44A and 44B by reason of the absence of forced air
injection, i.e., by the absence of a fan in heat recovery heat
exchanger 44C. In heat recovery heat exchanger 44C, the design of
the exhaust gas duct must be such that the gas turbine exhaust duct
acts as an ejector. That is to say, the velocity flow of the
exhaust gases in the vicinity of inlet section 62 of heat exchanger
44C must be large enough to produce a suction strong enough to draw
into the heat recovery heat exchanger sufficient ambient air to
achieve the desired cooling of the exhaust gases. Conventional
design parameters would be employed, and no excessive
experimentation would be required to achieve these results.
Control of the amount of ambient air drawn into heat recovery heat
exchanger 44C can be achieved by flap valve arrangement 71C
positioned at the entrance to inlet section 62 of heat recovery
heat exchanger 44C.
While the above detailed description refers to the use of an
organic working fluid, particularly those based on hydrocarbons,
the invention is also applicable to working fluids that are not
organic. For example, the invention is applicable to a water-based
system where the problem is to maintain a substantially fixed
vaporizing temperature for the heat recovery cycle in the face of
variable ambient condition, and where ambient temperatures do not
reach a temperature at which water freezes. Embodiment 80 of the
present invention shown in FIG. 4 is an example of a gas turbine
system with a water-based heat recovery cycle.
In embodiment 80, gas turbine system 12 produces hot exhaust gases
that pass through duct 81 to connection 82 that is connected to the
duct, the connection including pivotal flap-valve 83 that can be
selectively pivoted from a inoperative position shown in solid
lines in FIG. 4 to an operative position shown by the broken lines.
In its inoperative position, valve 83 permits the hot exhaust gases
to enter heat recovery heat exchanger means including vaporizer
component 85, for example, in the form of water tubes; and in its
operative position, valve 83 switches the hot gases to by-pass
stack 86. Normally, valve 83 would be in its inoperative position;
but the valve can be moved to its operative position whenever
maintenance must be performed on the heat recovery cycle equipment
or for other reasons.
Associated with heat recovery heat exchanger 84 is injector 87 that
operates in the same manner as injector 66. In this case, however,
the angular position of valve 71, and hence the amount of ambient
air mixed with the hot exhaust gases as determined by a control
signal generated by a temperature sensor as described below.
Alternatively, an arrangement similar to that shown in FIG. 3C can
be used.
The heat recovery heat exchanger means includes component 85 that
contains water which is vaporized by the mixture of hot exhaust
gases from the gas turbine unit and ambient air; and the steam
produced is supplied by line 90 to steam turbine 91. Cooled gases
downstream of the vaporizer component are vented to the atmosphere
through a suitable stack. The expansion of the steam produced by
steam turbine 91 drives generator 92 producing power; and expanded
steam exits the turbine and enters condenser 95, preferably air
cooled, for condensing the expanded steam into condensate. Pump 93
returns the steam condensate to heat recovery heat exchanger
84.
Temperature level sensor 89 associated with heat recovery heat
exchanger 84 produces a control signal functionally related to the
temperature difference of the gases entering heat exchanger 84 and
the preferred set temperature of these gases; and this control
signal is applied to control means 94 for controlling the position
of valve 95 thus establishing the temperature of the mixture of
exhaust gases and ambient air before the mixture enters into heat
exchange relationship with the heat recovery heat exchanger means
including the vaporizer component of the heat recovery heat
exchanger. In this manner, the temperature of the gas mixture can
be controlled to maintain a predetermined temperature for
vaporizing the water in the face of variable conditions that affect
the operation of heat recovery heat exchanger means 85 which
includes the vaporizer component.
In an alternative arrangement, condenser 95 may be replaced with a
bottoming, closed Rankine cycle organic fluid power plant as shown
in broken lines in FIG. 4. In such case, steam exhausted from
turbine 91 would be applied to indirect contact heat exchanger 96
containing an organic fluid which would be vaporized as a result.
The vaporized organic fluid is supplied to organic vapor turbine 97
coupled to a generator; and the expanded organic vapor exiting
turbine 97 is condensed in air-cooled condenser 98, the organic
fluid condensate being returned to steam condenser 96 by pump 99 to
complete the organic working fluid cycle. This arrangement is
particularly useful when steam condenser operation is to take place
at other than vacuum conditions.
The gas turbine unit constituted in accordance with the present
invention may be configured as shown in FIG. 5 by reference numeral
12A with intercooler 100 located between low pressure compressor 14
and high pressure compressor 16. Gas turbine 18, which is supplied
with combustion gases produced after fuel is burned in the presence
of compressed air produced by compressor 16, is coupled at 101 to
gas compressor 102 that receives gas from a production well (not
shown) or from a gas transmission pipeline, and compresses the gas
for delivery to a gas transmission line for further transport.
Three stages of gas compression are shown, and these are
representative of a typical gas pumping station at the origin of a
transmission pipeline, or intermediate the pipeline between the
well head and the terminus of the pipeline.
Gas to be compressed is supplied to low pressure compressor 103,
and the heated compressed gas is cooled in intercooler 104 before
being delivered to and compressed further in intermediate
compressor 105. The heated compressed gas is cooled in intercooler
106 before being delivered to and compressed further in high
pressure compressor 107. The heated compressed gas is cooled in
cooler 108 before being delivered to the gas transmission pipeline
(not shown). As indicated, some of the compressed gas is fed back
to the gas turbine unit and used to fuel the gas turbine
combustor.
The heat extracted from the compressed gas in intercoolers 104,
106, and 108 as well as the heat extracted from the compressed air
in intercooler 100, is converted into electricity by organic
converter 110. That is to say, in the configuration shown in FIG.
5, which is presented as an example of the utilization of heat
extracted by the intercoolers, organic fluid preheated in
intercooler 104, which is the low pressure intercooler for the gas
compressor, is vaporized in intercooler 100. Intercoolers 106 and
108 associated with the intermediate and high pressure compressors
of the gas compressor, also operate as vaporizers, and the outputs
of these vaporizers are supplied in parallel with the output of
intercooler 100 to organic vapor turbine 111 coupled to generator
112. After expansion of the vaporized organic fluid and the
consequent generation of power, the expanded organic vapor is
supplied to air condenser 111 wherein condensation takes place.
Pump 112 returns the organic condensate in parallel to intercoolers
104, 106, and 108 to complete the organic fluid cycle.
The above description of the present invention refers to the use of
an organic based, rather than a water based, working fluid for a
heat recovery cycle associated with a gas turbine, when ambient
temperatures are lower than the freezing point of water. The
present invention, however, is also particularly advantageous in
circumstances when the use of water, or its availability, is
problematic.
In addition, while the above description refers to using the heat
recovery cycle for producing electricity, the shaft power produced
by the turbine in the heat recovery cycle can alternatively be used
for directly driving equipment, such as gas compressors or running
such machinery, without converting the shaft power into
electricity.
Furthermore, an intermediate heat transfer fluid cycle can be used
in the heat recovery cycle for transferring the heat from the
exhaust gases of the gas turbine to an organic working fluid.
While the above description discloses a single organic working
fluid heat recovery cycle, the present invention includes the use
of cascaded, or parallel, operating units in a heat recovery cycle.
If cascaded units are used, the higher pressure turbine or turbines
may use water as a working fluid in closed cycles.
Moreover, while the above description discloses the use of adding
air to the exhaust gases of the gas turbine for controlling the
temperature of the gases from which heat is extracted in the heat
recovery cycle, if preferred, a power plant utilizing a simple
closed cycle organic Rankine cycle or cycles having an air cooled
condenser can be used wherein no air is mixed with the exhaust
gases of the gas turbine. By using such a closed, organic Rankine
cycle power plant for the heat recovery rather than a steam
turbine, the construction, operation, and maintenance of the
overall system is simplified permitting reliable and unattended
systems to operate for long periods of time at remote
locations.
The advantages and improved results furnished by the method and
apparatus of the present invention are apparent from the foregoing
description of the preferred embodiment of the invention. Various
changes and modifications may be made without departing from the
spirit and scope of the invention as described in the appended
claims.
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